#!/usr/bin/perl -w
use strict;

my $pid;
&start_gnuplot;

sub start_gnuplot{
  $pid = open(GP, "| '/usr/bin/gnuplot' 2>&1 "); 
  syswrite(GP, "plot sin(x)\n");
  sleep 2;
  syswrite(GP, "plot tan(x)\n");
  sleep 2;
  syswrite(GP, "quit\n");
}